At different stages in the life of a producing well it is necessary to perform interventions for repairs or modifications in the producing tubing assembly, modification of the producing zones by perforating or drilling new reservoir zones. These interventions can be performed without killing the well (filling the well with heavy fluids) and with pressure at the well head. A major concern in these types of interventions is to safely contain the well head pressure while deploying the interventions tools.
During interventions in producing wells, several interventions are usually done to maintain the producing tubing assembly, as for:                cleaning of the well bore        pumping of stimulation or cleaning fluids        milling restrictions        operations or repairs of valves.        
To enhance production, more zones of the reservoir can be put to production by                perforating new zones        drilling lateral drain holes        
It is often required to perform these interventions without killing the well to avoid damage to producing zones by invasion of killing fluids. This implies to keep the well under balanced or near balanced with produced fluids, gas or light fluids. This means that pressure will continually be present at the well head during the deployment, operation and retrieval of the downhole tools, umbilical and wireline cable.
Flow conduits used during interventions in underbalanced wells need to be designed following requirements for downhole operations, for example small cross section, resistance to wear, temperature and pressure, etc. However, deploying flow conduits under pressure requires the flow conduit to withstand large differential pressures, snubbing into a pressure barrier to overcome the effect of the pressure on the presented surface area, large buckling forces or large tensile forces, large gripping forces to prevent ejection from the well and coiling for relatively compact storage and transportation. These design requirements are difficult to satisfy completely because of the large safety coefficient required for surface equipment under pressure is often contradictory the requirements for downhole operation.
One existing means to perform these types of interventions is coil tubing, but this involves the use of very large and expensive surface equipment such as injectors and strippers. Also the safety coefficient for coil tubing is low and it is not widely accepted to circulate well fluids to surface with coil tubing. Very high stresses in coil tubing during deployment can lead to fatigue and possible failures not compatible with safe operation under pressure at surface. Another existing means to perform these types of interventions is pipe snubbing, but this system has several limitations in terms of time performance or safety.
Both coil tubing and pipe snubbing use existing tubular conduits. U.S. Pat. No. 6,217,975 describes a technology for the construction of tubular conduits from elongate strips of flexible material. These a rolled axially and the long edges joined to form a tubular conduit. U.S. Pat. No. 6,431,271 describes various uses for such a system in a wellbore environment.
It is the purpose of this invention to allow safe deployment and retrieval of a tool string, cable and flow conduit with formation induced well pressure at the well head using a compact and easily transportable system. This is achieved by forming the tubular conduit under borehole pressure, such as inside the wellhead system.